package mystack;

public class DoubleListNode {
    DoubleListNode pre;
    String val;
    DoubleListNode next;

    public DoubleListNode(String val) {
        this.val = val;
    }

    boolean hashNext(){
        return next!=null?true:false;
    }
    boolean hashPre(){
        return pre!=null?true:false;
    }
}
